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Iron (Fe) minerals possess a huge specific surface area and high adsorption affinity, usually considered as "rust tanks" of organic carbon (OC), playing an important role in global carbon storage. Microorganisms can change the chemical form of Fe by producing Fe-chelating agents such as side chains and form a stable complex with Fe(III), which makes it easier for microorganisms to use. However, in seasonal frozen soil thawing, the succession of soil Fe-cycling microbial communities and their coupling relationship with Fe oxides and Fe-bound organic carbon (Fe-OC) remains unclear. We characterized changes in the Fe phase, Fe-OC, Fe-oxidizing bacteria (FeOB), and Fe-reducing bacteria (FeRB) in the subsoil and analyzed the microbial mechanism underlying Fe-OC changes in alpine grassland by constructing a composite structural equation model (SEM). We found that the Fe(III) content consistently exceeded that of Fe(II). Among the three types of Fe oxides, organically complex Fe (Fep) decreased from 2.54 to 2.30 g·kg−1, whereas the opposite trend was observed for poorly crystalline Fe (Feo). The Fe-OC content also decreased (from 10.31 to 9.47 g·kg−1; p < 0.05). Fe-cycling microorganisms were markedly affected by the thawing of frozen soil (except FeRB). Fep and Feo directly affected changes in Fe-OC. Soil moisture (SM) and FeOB were significant indirect factors affecting Fe-OC changes. Freeze–thaw changes in the subsoil of alpine grassland in Central Asia significantly affected FeOB and Fe oxides, thus affecting the Fe-OC content. To the best of our knowledge, this was the first study to examine the influence of Fe-cycling microorganisms on the Fe phase and Fe-OC in the soil of alpine grassland in Central Asia. Overall, our findings provide scientific clues for exploring the biogeochemical cycle process in future climate change. [ABSTRACT FROM AUTHOR]

The ESA CCI Soil Moisture multi-satellite climate data record is a widely used dataset for large-scale hydrological and climatological applications and studies. However, data gaps in the record can affect derived statistics such as long-term trends, and – if not taken into account – can potentially lead to inaccurate conclusions. Here, we present a novel gap-free dataset, covering the period from January 1991 to December 2023. Our dataset distinguishes itself from other gap-filled products, as it is purely based on the available soil moisture measurements (independent of ancillary variables to make predictions), and further due to the inclusion of uncertainty estimates for all interpolated data points. Our gap-filling framework is based on a well-established univariate Discrete Cosine Transform with Penalized Least Squares (DCT-PLS) algorithm. This ensures that the dataset remains fully independent of other soil moisture and biogeophysical datasets, and eliminates the risk of introducing non-soil moisture features from other variables. We apply DCT-PLS on a spatial moving window basis to predict missing data points based on temporal and regional neighbourhood information. The challenge of providing gap-free estimates during extended periods of frozen soils is addressed by applying a linear interpolation for these periods, which approximates the retention of frozen water in the soil. To quantify the inherent uncertainties in our predictions, we developed an uncertainty estimation model that considers the input observations quality and the performance of the gap-filling algorithm under different surface conditions. We evaluate our algorithm through performance metrics with independent in situ reference measurements and by its ability to restore GLDAS Noah reanalysis data in artificially introduced satellite-like gaps. We find that the gap-filled data performs comparable to the original observations in terms of correlation and ubRMSD with in situ data (global median R = 0.72, ubRMSD = 0.05 m 3 m -3. However, in some complex environments with sparse observation coverage, performance is lower. The new ESA CCI SM v09.1 GAPFILLED dataset is publicly available at https://doi.org/10.48436/s5j4q-rpd32 (Preimesberger et al., 2024) and will see yearly updates due to its inclusion in the operational ESA CCI SM production. [ABSTRACT FROM AUTHOR]

In cold regions, the frozen soil–rock mixture (FSRM) is subjected to cyclic loading coupled with freeze–thaw cycles due to seismic loading and ambient temperature changes. In this study, in order to investigate the dynamic mechanical response of FSRM, a series of cyclic cryo-triaxial tests were performed at a temperature of −10 °C on FRSM with different coarse-grained contents under different loading conditions after freeze–thaw cycles. The experimental results show that the coarse-grained contents and freeze–thaw cycles have a significant influence on the deformation properties of FSRM under cyclic loading. Correspondingly, a novel binary-medium-based multiscale constitutive model is firstly proposed to describe the dynamic elastoplastic deformation of FSRM based on the coupling theoretical framework of breakage mechanics for geomaterials and homogenization theory. Considering the multiscale heterogeneities, ice-cementation differences, and the breakage process of FSRM under external loading, the relationship between the microscale compositions, the mesoscale deformation mechanism (including cementation breakage and frictional sliding), and the macroscopic mechanical response of the frozen soil is first established by two steps of homogenization on the proposed model. Meanwhile, a mixed hardening rule that combines the isotropic hardening rule and kinematic hardening is employed to properly evaluate the cyclic plastic behavior of FSRM. Finally, comparisons between the predicted results and experimental results show that the proposed multiscale model can simultaneously capture the main feature of stress–strain (nonlinearity, hysteresis, and plastic strain accumulation) and volumetric strain (contraction and dilatancy) of the studied material under cyclic loading. [ABSTRACT FROM AUTHOR]

Horizontal frost damage is a significant hazard threatening the safety of structures in cold regions. The frozen fringe represents the transitional zone between unfrozen and frozen soil. Its formation and migration not only directly influence the distribution of water during freezing but also play a significant role in the frost heave behavior. This study employed self-developed horizontal frost heave equipment to conduct seven experiments, exploring the effects of initial water content and dry density on the development of the frozen fringe in kaolin clay. As the initial water content increases, the water migration speed accelerates, and frost heave increases. The experimental results show that for every 5% increase in initial water content, the frost heave increases by an average of 3.43 mm. With increasing initial dry density, frost heave decreases, and the water migration speed decreases. For every 0.1 g/cm3 increase in initial dry density, the frost heave increases by an average of 3.26 mm. The study also found that the frozen fringe does not strictly advance in the vertical direction, which may have a potential impact on the structural integrity. Based on these experimental results, this study proposes an improved method for predicting the frozen fringe using the freezing point, building upon the Mizoguchi model, and validates its accuracy with field data. The research provides a theoretical basis for the design of slopes, retaining walls, and foundation pits, as well as for the implementation of frost heave prevention measures in cold regions. [ABSTRACT FROM AUTHOR]

Pipelines are the primary mode of oil and gas transport in cold regions. Differential frost heaving of frozen and non-frozen soil masses can damage such pipelines, posing economic and environmental risks. The present study investigates the mechanical behaviors of buried pipelines under differential frost heaving forces. A discrete forecasting model of these mechanical behaviors based on frost heaving springs is proposed. The relationship between the frost heaving amount and force at any moment is established using the Takashi empirical equation and the corresponding development of frost depth. On this basis, the properties of nonlinear frost heaving springs are disclosed. A model of pipeline mechanical state is derived to understand the deformation and stress at any moment, allowing the dynamic prediction of mechanical behaviors. The model is applied to two case studies involving the Caen and Alaska buried pipelines. The modeling results agree well with measurements taken at these pipelines, and the discrete descriptions of their mechanical modes are effective. A sensitivity analysis of the modeling results for pipelines of different size was conducted, providing a theoretical foundation for the optimal design of buried pipelines in cold regions. [ABSTRACT FROM AUTHOR]

In the framework of sustainable development and environmental preservation, this research aims to improve the stability and frost resistance of sulfate saline soil by utilizing industrial solid waste. Geopolymer materials containing fly ash (FA) activated by different NaOH concentrations were studied for study on stabilized soil with saline soil, with NaOH concentrations used ranged from 0.1 to 0.9. This study investigates the impact of the molar concentration of NaOH and the number of freeze-thaw cycles on the microstructure and strength of stabilized soil incorporating FA geopolymer. The XRD, FTIR, and TG studies of NaOH-excited FA stabilized soil revealed that the FA gel material grew with increasing concentration. The strength and frost resistance of stabilized soil increased and then declined as NaOH concentration increased, with an optimum excitation concentration of 0.5 M. After 28 days of curing at 20 °C, its UCS and splitting strength were 7.18 MPa and 1.89 MPa, respectively. The residual values of UCS and splitting strength after 5 freeze-thaw cycles (12 hours of freezing followed by 12 hours of thawing at +20 °C) at the optimal concentration were 46.35% and 39.92%, respectively. [ABSTRACT FROM AUTHOR]

Purpose: Soil freeze-thaw is a common phenomenon at high latitude regions, and it can alter soil physical properties and microbial diversity. However, how the abundant and rare fungal groups respond to environmental temperature changes (i.e., seasonal variations), particularly freeze-thaw events, are still not well understood. Methods: In this study, we investigated the dynamics of soil properties, fungal community diversity, structure, and co-occurrence network in a typical seasonally frozen ecosystem. We sampled three times during the non-freeze-thaw, freeze-thaw, and freezing periods, respectively. Results: Our findings revealed that significant variations in the fungal community diversity were detected among different sampling periods. Notably, compared to the non-freeze-thaw and freeze-thaw periods, soil freezing significantly increased the alpha diversity of abundant and rare fungal taxa. We also found that the abundance of rare taxa was important to promote the stability of fungal co-occurrence network. Soil moisture, organic carbon, total nitrogen, and total phosphorus content were the primary factors affecting fungal community composition and structure. Although soil pH had no significant impact on fungal community structure, it exhibited significant correlations with some rare taxa. Conclusion: Overall, the study results provide the useful information on the prediction of soil fungal community in response to environmental temperature changes in seasonally frozen ground. [ABSTRACT FROM AUTHOR]

In this theoretical paper, a method for temperature profile retrieval in frozen tundra soil is proposed based on the thermoevolutionary relationship between polarimetric multi-angular brightness temperature (TB) at 1.4 GHz, observed in sliding time window with a fixed duration, and the time series of soil temperature profiles, predicted by the heat equation. For TB modelling, the profiles of volumetric moisture, dry bulk density, and organic matter content in the active layer, measured at the Franklin Bluffs test site (North slope of Alaska, U.S.) from 12 December 2022 to 5 May 2023, were used. When solving the inverse problem, the retrieving temperature profiles were specified as a linear interpolation function between four known depths 0 cm, 25 cm, 50 cm, and 95 cm. The thermodynamic properties of the frozen active layer were considered independent of soil temperature, time, and vertical coordinates, which made it possible, based on weather station data, to determine the apparent value of the thermal diffusivity coefficient in the heat equation. The practically significant accuracy of retrieving soil temperature up to a depth of 70 cm with a root-mean-square error of 0.5–1.8°C and a coefficient of determination of 0.877–0.988 was demonstrated by the proposed method. The pursued research shows the advantage of the synergy of the heat equation and polarimetric multi-time compared to only single-moment TB observations for temperature profile retrieval in frozen tundra soil. [ABSTRACT FROM AUTHOR]

The article addresses the issue of numerical modeling of the process of forming the temperature regime of earth dams, along with their foundations, built and operated in permafrost conditions. A large number of such structures have been constructed in the permafrost regions of the Earth to meet the needs of industry and population. The paper outlines the key principles of designing and constructing such structures. These principles were developed based on years of experience in hydrotechnical construction. Failure to follow these principles leads to structural failures, as confirmed by the presented statistics on accidents. It is essential to ensure the appropriate thermal condition of the structure and its foundation, either frozen or thawed. An unplanned transition of soils from one state to another may lead to an emergency situation. Temperature changes can cause phase transitions of water from liquid to solid (ice), which also affects the formation of the structure's regime. Numerical methods of calculation allow for the most comprehensive consideration of the influencing factors and processes. The article presents the results of numerical modeling of the filtration-temperature regime of an earth dam with a foundation in permafrost conditions, using two computational programs. The first is based on a locally variational approach (Termic, authored by the researchers), while the second uses a classical linear equation system solution (PLAXIS 2D 2022 software). A comparison of the results obtained from both programs showed good qualitative and quantitative consistency. Under the influence of seepage flow, the zone of frozen ground degradation is spreading in the lower part of the earth dam and its foundation. By September of the 27th year of operation, the thawed ground zone reaches approximately the middle of the structure at the base. The temperature values along the screen axis at the base of the structure are +1.2 °C (according to the Termic program—ver. 1.1) and +1.06 °C (according to PLAXIS 2D PC). Recommendations and future research directions on this topic are also formulated. [ABSTRACT FROM AUTHOR]

In the remediation process of heavily metal-contaminated soil, biochar can change the ion content and soil structure, significantly impacting soil freezing. This experiment used freezing ambient temperature, water (W) content, heavy metal (M) contents, and biochar (BC) contents as factors affecting soil freezing. The test soil was manually compacted in a homemade acrylic device to achieve a compaction level of 90%. The temperature changes of the soil during low-temperature freezing were monitored through thermometry experiments. The results indicated that soil freezing temperature decreased with increasing heavy metal and biochar contents and increased with increasing initial water content and freezing ambient temperature. Multiple freeze–thaw cycles revealed the interaction between biochar and heavy metals. The effects of biochar on the freezing temperature of soil with different heavy metal contents were different; in the soil with the same heavy metal content, 3% biochar contents had little effect on the freezing temperature of heavy metal-polluted soil, and 5% and 7% biochar contents significantly improved the freezing resistance of the soil. Freeze–thaw cycling had little effect on the soil's microporous structure, resulting in minimal changes in soil freezing temperatures after seven cycles. Correlation analyses of heavy metals, water content, and biochar revealed that the effects of these factors on freezing temperature were in the order of heavy metals > water > biochar. The composite freezing temperature of biochar and heavy metal overlaps well. The initial freezing temperature of the soil was used to predict the unfrozen water in the soil. The prediction results showed that biochar increased the content of unfrozen water in the soil. [ABSTRACT FROM AUTHOR]

Permafrost regions of Qilian Mountains in China are rich in gas hydrate resources. Once greenhouse gases in deep frozen layer are released into the atmosphere during hydrate mining, a series of negative consequences occur. This study aims to evaluate the impact of hydrate thermal exploitation on regional permafrost and carbon budgets based on a multi-physical field coupling simulation. The results indicate that the permeability of the frozen soil is anisotropic, and the low permeability frozen layer can seal the methane gas in the natural state. Heat injection mining of hydrates causes the continuous melting of permafrost and the escape of methane gas, which transforms the regional permafrost from a carbon sink to a carbon source. A higher injection temperature concentrates the heat and causes uneven melting of the upper frozen layer, which provides a dominant channel for methane gas and results in increased methane emissions. However, dense heat injection wells cause more uniform melting of the lower permafrost layer, and the melting zone does not extend to the upper low permeability formation, which cannot provide advantageous channels for methane gas. Therefore, a reasonable and dense number of heat injection wells can reduce the risk of greenhouse gas emissions during hydrate exploitation. [ABSTRACT FROM AUTHOR]

The thawing of frozen soils has resulted in the release of tremendous amounts of organic carbon. Permafrost-derived dissolved organic carbon (DOC) has been demonstrated to be biolabile to microbes in aquatic ecosystems. Cladoceran grazing is another regulatory force that may affect the properties and/or characteristics of the bacterial community. However, the effects of permafrost DOC and cladoceran grazing on bacterial abundance, community composition, and diversity in aquatic ecosystems have rarely been explored. In this study, DOC was extracted from frozen soils adjacent to the shoreline of a pristine alpine lake and used to culture bacteria. The bacterial abundance decreased over time during the bioincubation experiment, whereas Daphnia feeding had no significant effect on the bacterial abundance. The genera Pedobacter, Novosphingobium, Flavobacterium and Limnohabitans had relatively high abundances after a 27-d bioincubation period. The overall decrease in bacterial diversity in the Daphnia grazing experiment was higher than that in the bacterial incubation experiment. The co-occurrence network demonstrated that terrestrial and microbial humic-like components C1 and C2 had strong interactions with Pseudolabrys, and tyrosine-like component C3 presented -correlations with Hyphomicrobium and Vampirovibrio. Bacterial communities in the two experiments were significantly different. Sphingomonadales, Sphingobacteriales, Burkholderiales, and Actinomycetales were the primary contributors to these differences. Our study contributes significantly to a broader understanding of carbon cycling and microbial food web in lakes, particularly in high-altitude and polar lakes. [ABSTRACT FROM AUTHOR]

A vast amount of waste disposable face masks (FM) has threatened the ecosystem since COVID-19 became a pandemic. Given the urgency of the situation, this study innovatively assessed the potential utilization of the waste FM fibers to reinforce the subgrade in the permafrost regions. The effect of FM contents (0.5%, 1%, and 1.5%) and length–width (LW) ratios (1, 2, and 3) of the frozen silty clay specimens (−10°C) with different initial moisture contents (w = 15%, 20%, and 25%) on the mechanical behavior, including the peak deviatoric stress (q), the increment of peak deviatoric stress (λ), and the initial elastic modulus (E0), was analyzed. The pore structure change mechanism under the influence of FM and w was further revealed via nuclear magnetic resonance (NMR). The results indicated that the incorporation of FM improved the soil strength at a certain w, while the FM content and LW ratio were found to have different effects on the q values. The most effective reinforcement can be identified at w = 20%, according to the relatively large λ values (29.2%–79.1%). Moreover, the E0 values of specimens with higher initial moisture content and FM content were smaller, which can be explained by the cracks generated due to the water-ice phase change and uneven distribution of FM. NMR results revealed that the FM had less effect on the pore-water relaxation characteristics, and the change in soil structure was more remarkable in the frozen specimens with higher w. This study pointed out that the tension of FM and its bonding soil particles played the leading role in soil stress–strain behavior. Practical Applications: The results of this study recommend that waste face masks (FM) be added to the soil in the subgrade to improve its strength in permafrost regions. The mechanical properties (including the peak deviatoric stress and initial elastic modulus) of soils reinforced by various FM contents and different FM sizes were determined via experiments. The reinforcing mechanism is discussed by observing the surface of frozen soils and detecting the change in pore structure before and after freeze–thaw to explain the complex mechanical behavior of reinforced soils. The moisture content of soils is a significant factor influencing the reinforcement effect. According to the test results, different reinforcement parameters, for example, the content of additive FM and the FM size, should be selected in the specimens with different moisture contents for the best reinforcement effect. This paper provides novel and valuable guidance for waste FM utilization and subgrade strengthening in permafrost areas. [ABSTRACT FROM AUTHOR]

To investigate the dynamic mechanical response and damage evolution behavior of ice-rich frozen clay, split Hopkinson pressure bar (SHPB) tests were performed on frozen clay specimens with initial moisture contents of 20%–1,000% under different temperatures, strain rates, and stress states. The stress–strain curves, dynamic strength, peak strain, absorbed energy density, failure mode, and failure progress were studied. The experimental results revealed the following: (1) in the radial-free state, the stress–strain curve of frozen clay with initial moisture contents ranging from 20% to 85% and 1,000% could be divided into three stages: elasticity, plasticity, and failure. In addition, a double peak phenomenon occurs in the stress–strain curves within the initial moisture content range of 120%–480%. (2) In the radial-free state, as the initial moisture content increased, the dynamic strength first increased to a maximum value, then decreased to a minimum value less than the dynamic strength of ice, and eventually increased marginally to the dynamic strength of ice. However, the variation in dynamic peak strain with initial moisture content followed a decrease–increase–decrease three-stage pattern. (3) In the passive confining pressure state, the initial moisture content of frozen soil determined its sensitivity to the confining pressure. (4) The high-speed camera test results indicated that the failure of the ice-rich frozen clay was mainly caused by tensile cracks. The degree of failure of the frozen clay specimens became more evident as the moisture content and strain rate increased. In the passive confining pressure state, the ice-rich frozen clay specimens remained intact except for a small amount of edge peeling. [ABSTRACT FROM AUTHOR]

The existing theories or numerical models of thaw consolidation for frozen soil rarely consider the influence of the thermal effect, so it is difficult to analyze the problem of thaw thermoconsolidation for frozen soil under high temperature. Using the piecewise linear approach and finite-difference method, a one-dimensional large strain thaw thermoconsolidation model, called TTCS1, is established for frozen saturated soil under high temperature. The model couples the heat transfer with phase change of frozen soil and the thermoconsolidation deformation, and accounts for the nonlinear changes of soil parameters and large strain during the process of thaw thermoconsolidation under high temperature. When the thermal effect is ignored, TTCS1 shows excellent agreement with the existing large strain thaw consolidation model. When the thermal effect is considered, the numerical solutions of the TTCS1 model are basically consistent with the test values. The influences of the thermal effect, boundary temperature, and boundary conditions on the thaw thermoconsolidation for frozen silty clay are further discussed, and the settlement and settlement rate of frozen soil under high temperature will be significantly underestimated if the thermal effect is not considered. [ABSTRACT FROM AUTHOR]

Modeling peatland hydraulic processes in cold regions requires defining near-surface hydraulic parameters. The current study aims to determine the soil freezing and water characteristic curve parameters for organic soils from peatland-dominated permafrost mires. The three research objectives are as follows: (i) Setting up an in situ soil freezing characteristic curve experiment by installing sensors for measuring volumetric water content and temperature in Storflaket mire, Abisko region, Sweden; (ii) Conducting laboratory evaporation experiments and inverse numerical modeling to determine soil water characteristic curve parameters and comparing three soil water characteristic curve models to the laboratory data; (iii) Deriving a relationship between soil freezing and water characteristic curves and optimizing this equation with sensor data from (i). A long-lasting in situ volumetric water content station has been successfully set up in sub-Arctic Sweden. The soil water characteristic curve experiments showed that bimodality also exists for the investigated peat soils. The optimization results of the bimodal relationship showed excellent agreement with the soil freezing cycle measurements. To the best of our knowledge, this is one of the first studies to establish and test bimodality for frozen peat soils. The estimated hydraulic parameters could be used to better simulate permafrost dynamics in peat soils. [ABSTRACT FROM AUTHOR]

Many experiments and computational techniques have been employed to explain the mechanical properties of frozen soils. Nevertheless, due to the substantial complexity of their responses, modeling the stress–strain characteristics of frozen soils remains challenging. In this study, artificial neural networks (ANNs) were employed for modeling the mechanical behavior of frozen soil, while different testing strategies were carried out. A database covering stress–strain data from frozen sandy soil subjected to varying temperatures and confining pressures, resulting from triaxial tests, was compiled and employed to train the model. Subsequently, different artificial neural networks were trained and developed to estimate the deviatoric stress and volumetric strain, while temperature, axial strain, and confining pressure were considered as the main input variables. Based on the findings, it can be indicated that the models effectively predict the stress–strain behavior of frozen soil with a significant level of accuracy. [ABSTRACT FROM AUTHOR]

Accurate and fast measurements of thermal properties are frequently required for characterizing the heat‐water dynamics in frozen soil. Measuring the thermal properties of frozen soil without inducing ice thaw has proven challenging with conventional heat pulse (HP) methods. In this study, based on an Infinite Line Source (ILS) semi‐analytical model that applies a constant temperature lower than the freezing point at the heat source to prevent the initiation of ice thaw in the frozen soil, we propose a novel HP‐based approach to measure thermal properties, applicable at temperatures below or above 0°C. Laboratory experiments and numerical modeling were utilized to validate the applicability of the approach and optimization strategies of the measurement. We found that the proposed HP‐based approach effectively maintained the maximum spatial temperature below the freezing point and therefore estimated the bulk thermal properties of quartz sand and ice contents. An optimized measurement strategy was proposed to monitor the temperature variations 2–4 cm away from the center of the heat probe after 60 s. This progress can largely facilitate the determination of the thermal properties of multi‐phase and ‐component frozen soil such as thermal conductivity, heat flux, and ice content in cold areas across soil science, hydrology, engineering, and climate science. Plain Language Summary: Frozen soil thermal properties are essential for understanding the potential impacts of varying temperatures on water and heat exchange within the surface soil and the subsurface environment. The conventional method, using the single pulse heating strategy to measure the thermal properties of frozen soil, has difficulty avoiding the ice‐melt process. Ice melt may lead to biased outputs due to the ice melting around the heating probe. In this study, we proposed a novel method to maintain a constant temperature on the heat source surface to avoid the overheating challenge within the measurement. The mathematical model and the proposed workflow can successfully estimate the bulk soil thermal conductivity, heat flux, and soil ice content in cold regions. Key Points: A novel approach has been developed using an Infinite Line Source model to predict frozen soil thermal properties and water/ice contentsThe proposed method offers distinct advantages for measurements, especially in frozen soil with temperatures near the freezing pointFurther application is valuable regarding its potential merits in minimizing ice melting in the measurement [ABSTRACT FROM AUTHOR]

Spring snowmelt has a significant impact on the hydrological cycle in seasonally frozen soil areas. However, scholars hold differing, and even opposing, views on the role of snowmelt during the thawing period in groundwater recharge. To explore the potential recharge effects of spring snowmelt on groundwater in seasonal frozen soil areas, this study investigated the vadose zone dynamics controlled by soil freeze–thaw processes and snowmelt infiltration in the Northeast of China for 194 days from 31 October 2020 to 12 May 2021. Responses of groundwater level and soil moisture to snowmelt infiltration show that most snowmelt was infiltrated under the site despite the ground being frozen. During the unstable thawing period, surface snow had already melted, and preferential flow in frozen soil enabled the recharge groundwater by snowmelt (rainfall), resulting in a significant rise in groundwater levels within a short time. The calculated and simulated snowmelt (rainfall) infiltration coefficient revealed that during the spring snowmelt period, the recharge capacity of snowmelt or rainfall to groundwater at the site is 3.2 times during the stable thawing period and 4.5 times during the non-freezing period. [ABSTRACT FROM AUTHOR]

Permafrost, as a soil type under unique environmental conditions, has bearing characteristics that are highly susceptible to thermo-hydraulic environments. Rapid evaluation of the bearing characteristics of in situ permafrost at various depths in perennially frozen regions is a critical scientific issue urgently needing resolution in the road design and construction sectors in China. To address this, this study investigates the correlation between CPT parameters and laboratory mechanical indices under the combined effects of multiple factors in frozen sandy soils. By conducting both CPT and CBR tests on frozen sandy soils, the study analyzes the trends in changes in cone tip resistance (qc) and CBR values under the influence of temperature (T), moisture content (ω), and compaction degree (K) and establishes a functional relationship between them. Based on the standard requirements for indoor CBR, an evaluation criterion using qc for assessing the bearing capacity of frozen sandy soil is proposed. The results indicate that both CBR values and qc increase initially and then stabilize as K increases. With decreasing temperature, both indices stabilize after an initial increase, with turning points at −3.1 °C for CBR values and −2.5 °C for qc. As ω increases, both indices first increase and then stabilize, with a turning point at 40%ω. There is a robust linear relationship between the CBR values and qc, with the ratio of predicted CBR values to actual values showing a histogram and log-normal distribution accounting for 81% and 51.3%, respectively, within a 20% accuracy level, indicating good predictive performance. Referring to the highway subgrade specifications for indoor CBR, a standard for evaluating the bearing capacity of frozen sandy soils using CPT technology is proposed. This study provides new insights for geological surveys in perennially frozen regions and a theoretical basis for the application of CPT technology in evaluating the bearing capacity of permafrost. [ABSTRACT FROM AUTHOR]

The interaction between the structure and soil is a crucial factor in infrastructure stabilization in cold region engineering, both transversely and vertically. During interface deformation, the transverse action is reflected in the change of constraints, including normal stiffness, normal stress, and normal volume, while the vertical action is reflected in the change of shear properties. However, the study of different transverse constraints is not systematic, especially considering the normal stiffness and shear properties at different hydrothermal states. This study investigated the shear behavior of the interface between concrete and frozen soil under different normal stiffness, temperature, and water content using the interface direct shear test under temperature‐controlled conditions. The results show that with the increase in temperature and water content, the initial shear stiffness of the interface shear stress‐shear displacement curve gradually increases, and the interface shear strength gradually increases. Different normal stiffnesses have a small effect on the morphology of the interfacial shear stress‐shear displacement curve but significantly affect the peak shear strength. The peak shear strength increases significantly with the increase of normal stiffness, and this trend is more obvious with the decrease in temperature. The corresponding interfacial cohesion and friction angle also increases with the increase in normal stiffness. [ABSTRACT FROM AUTHOR]

Changes in the hydrothermal regime of soils caused by the melting of the permafrost layer are the most important ecological factor in the dynamics of vegetation in the cryolithozone. The impact of soil thawing on the growth index (GI) of larch (Larix spp.) and on the gross and net primary productivity (GPP and NPP) of vegetation in the Arctic region of Central Siberia (sparse forests, tundra, and forest tundra) is investigated. The following hypotheses are tested: (1) gravimetric data allow us to assess the dynamics of water mass in soils; (2) thawing of frozen soils stimulates the growth of woody plants and the productivity of vegetation. This work uses methods of dendrochronology, field data, satellite gravimetry (GRACE survey), and remote sensing of GPP (Terra/MODIS survey). An analysis of gravimetric data has revealed a significant long-term trend of decreasing water mass in soils of the cryolithozone (R2 = 0.68). The amount of water released during melting is estimated at 6.4 ± 2.3 kg/m–2 per year. A close relationship was established between the GI of larch and GPP with moisture anomalies in soils (r = –0.7 and r = –0.9, respectively). The increasing temperature of the root zone and the deficit of water vapor moisture also have a positive effect on the GI of larch and the GPP value of vegetation as a whole (r = 0.6 and r = 0.6–0.9, respectively). It is established that pyrogenic carbon losses are significantly (two orders of magnitude) lower than the NPP value. Under conditions of waterlogged soils, which are typical for the Arctic, climate warming is accompanied by an improvement in the hydrothermal growth regime of the plant cover and contributes to an increase in the productivity of vegetation and the preservation of the cryolithozone status of a carbon sink area. [ABSTRACT FROM AUTHOR]

Due to the large temperature fluctuations between day and night during the transition from winter to spring, soil sites in seasonally frozen soil areas go through repeated freeze–thaw cycles. During these cycles, the water in the soil undergoes phase transformation and migration, which changes the physical and mechanical properties of the soil and directly affects the stability and durability of the soil site. In order to explore the feasibility of using the ZDS-2 organosilicon reinforcement agent for the anti-freeze-and-thaw protection of soil sites, Qingtai site soil and the ZDS-2 organosilicon reinforcement agent were used as raw materials. The optimal ratio of modified soil samples with different freeze–thaw cycles was obtained by laboratory tests. The strengthening mechanism of the ZDS-2 organosilicon reinforcement agent under freeze–thaw cycles was revealed by a microscopic test. The test results showed that the ZDS-2 organosilicon reinforcement agent can inhibit the volume expansion of soil samples caused by the freeze–thaw cycle. After nine freeze–thaw cycles, the shear strength of the soil samples, to which 15% ZDS-2 organosilicon reinforcement agent was added, increased by 53.4% on average compared with plain soil. The highly cross-linked organic–inorganic hybrid network structure formed between the siloxane group in the ZDS-2 organosilicon reinforcement agent and the soil particles can fill the pores and form a protective layer. The experimental results provided a basis and reference for the research of freeze–thaw-resistant materials for soil sites in seasonally frozen soil areas. [ABSTRACT FROM AUTHOR]

Recent advancements in underground construction have led to the widespread utilization of pipe jacking. However, the engineering challenges posed by frozen ground in pipe jacking projects have not been extensively studied. This research aims to address the critical challenges linked to employing pipe jacking in frozen ground for underground construction. It is widely recognized that the accurate calculation of jacking thrust and mitigation of pipe–soil interaction plays a crucial role in determining the success or failure of pipe jacking operations. To explore these issues, this study conducted numerical simulations and comparative analyses, considering various factors such as soil properties, geometric dimensions, and burial depth, to assess their influence on jacking thrust. Additionally, the study also examines the freeze–thaw effect on concrete pipes and the injected lubricant. The results indicate that the numerical model, which considers the temperature effects and static friction instead of sliding friction, provides a more reliable estimation of jacking thrust in frozen ground compared to traditional theoretical models. Furthermore, the freezing point depression method was successfully employed in the development of an anti-freezing lubricant, which can effectively reduce pipe–soil interaction even at extremely low temperatures of up to −10 °C. [ABSTRACT FROM AUTHOR]

Fresh submarine groundwater discharge (FSGD) can deliver significant fluxes of water and solutes from land to sea. In the Arctic, which accounts for ∼34% of coastlines globally, direct observations and knowledge of FSGD are scarce. Through integration of observations and process‐based models, we found that regardless of ice‐bonded permafrost depth at the shore, summer SGD flow dynamics along portions of the Beaufort Sea coast of Alaska are similar to those in lower latitudes. Calculated summer FSGD fluxes in the Arctic are generally higher relative to low latitudes. The FSGD organic carbon and nitrogen fluxes are likely larger than summer riverine input. The FSGD also has very high CO2 making it a potentially significant source of inorganic carbon. Thus, the biogeochemistry of Arctic coastal waters is potentially influenced by groundwater inputs during summer. These water and solute fluxes will likely increase as coastal permafrost across the Arctic thaws. Plain Language Summary: Groundwater flows from land to sea, transporting freshwater, organic matter, nutrients, and other solutes that impact coastal ecosystems. However, along coasts of the rapidly‐warming Arctic, there is limited knowledge regarding how much fresh groundwater enters the ocean. Using field observations and numerical models, we show that groundwater flowing from tundra in northern coastal Alaska carries large amounts of freshwater, organic matter, and carbon dioxide to the Arctic lagoons during summer. These inputs are likely significant to coastal biogeochemical cycling and marine food webs. Groundwater discharge and the associated transport of dissolved materials are expected to increase due to longer periods of above‐zero temperatures that thaw frozen soils below the tundra. Key Points: Summer fresh submarine groundwater discharge (FSGD) to the Alaskan Beaufort Sea is only 3%–7% of rivers but carries as much organic matterSummer FSGD delivers a median of 116 (interquartile range: 35–405) and 6 (2–21) kg/d per km dissolved organic carbon and nitrogenFresh groundwater at the beach of Simpson Lagoon (SL) has a median PCO2 of ∼33,000 μatm implying substantial CO2 flux [ABSTRACT FROM AUTHOR]

Salt expansion and frost heave are the main diseases of salted frozen soil roadbeds. Salt swelling and frost heave disease are closely related to the salted soil water–salt migration, temperature variation, and salt crystallization amount change. This article establishes a coupled model of water, heat, and salt fields based on the capillary model and the unfrozen water characteristic curve. The study shows that the different initial moisture contents have minimal effects on the location of soil salt migration and aggregation. The different initial salt concentrations have a substantial effect on the soil water–salt migration aggregation position; when the concentration of sodium sulfate increases, different from chloride saline soils, the position of the freezing front fluctuates up and down over time. The water–salt migration and aggregation are smaller in the closed condition, where they are reduced by 38% and 20%, respectively. [ABSTRACT FROM AUTHOR]

As the interface between frozen and unfrozen soil, the ice front is not only a spatial location concept, but also a potentially dangerous interface where the mechanical properties of soil could change abruptly. Accurately identifying its spatial position is essential for the safe and efficient execution of large-scale frozen soil engineering projects. Electrical capacitance tomography (ECT) is a promising method for the visualization of frozen soil due to its non-invasive nature, low cast, and rapid response. This paper presents the design and optimization of a mobile circular capacitance sensor (MCCS). The MCCS was used to measure frozen soil samples along the depth direction to obtain moisture distribution and three-dimensional images of the ice front. Finally, the experimental results were compared with the simulation results from COMSOL Multiphysics to analyze the deviations. It was found that the fuzzy optimization design based on multi-criteria orthogonal experiments makes the MCCS meet various performance requirements. The average permittivity distribution was proposed to reflect moisture distribution along the depth direction and showed good correlation. Three-dimensional reconstructed images could provide the precise position of the ice front. The simulation results indicate that the MCCS has a low deviation margin in identifying the position of the ice front. [ABSTRACT FROM AUTHOR]

The snow melting and runoff process in the black soil area of Northeast China has led to soil quality degradation in farmland, posing a threat to sustainable agricultural development. To investigate the regulatory effect of tillage layer construction on the infiltration characteristics of snowmelt water, a typical black soil in Northeast China was selected as the research object. Based on field experiments, four protective tillage treatments (CK: control treatment; SB: sub-soiling treatment; BC: biochar regulation treatment; SB + BC: sub-soiling tillage and biochar composite treatment) were set up, and the evolution of soil physical structure, soil thawing rate, snow melting infiltration characteristics, and the feedback effect of frozen layer evolution on snowmelt infiltration were analyzed. The research results indicate that sub-soiling and the application of biochar effectively regulate soil aggregate particle size and increase soil total porosity. Among them, at the 0–10 cm soil layer, the soil mean weight diameter (MWD) values under SB, BC, and SB + BC treatment conditions increased by 6.25%, 16.67%, and 19.35%, respectively, compared to the CK treatment. Sub-soiling increases the frequency of energy exchange between the soil and the environment, while biochar enhances soil heat storage performance and accelerates the melting rate of frozen soil layers. Therefore, under the SB + BC treatment conditions, the maximum soil freezing rate increased by 21.92%, 5.67%, and 25.12% compared to the CK, SB, and BC treatments, respectively. In addition, sub-soiling and biochar treatment effectively improved the penetration performance of snowmelt water into frozen soil layers, significantly enhancing the soil's ability to store snowmelt water. Overall, it can be concluded that biochar regulation has a good improvement effect on the infiltration capacity of surface soil snowmelt water. Sub-soiling can enhance the overall snowmelt water holding capacity, and the synergistic effect of biochar and deep tillage is the best. These research results have important guiding significance for the rational construction of a protective tillage system model and the improvement of the utilization efficiency of snowmelt water resources in black soil areas. [ABSTRACT FROM AUTHOR]

The editorial discusses the mechanical properties and engineering applications of special soils, such as soft soil, loess, and frozen soil, which present challenges in geotechnical design and construction globally. The study emphasizes the importance of understanding the unique characteristics of special soils to ensure safe and cost-effective engineering practices. Various research papers in the Special Issue explore topics like shear rate effects on clayey soil, fiber reinforcement in soft clay, and the impact of different loading methods on expansive soil, contributing to advancements in soil mechanics research. The findings aim to enhance engineering quality and safety through effective measures and novel materials, with a focus on practical engineering applications. [Extracted from the article]

Featured Application: The nonlinear autoregressive with exogenous input (NARX) network model developed in this study provides an advanced solution for accurately predicting subgrade temperatures in seasonally frozen regions. This model can be directly applied to infrastructure projects, such as road and railway construction, where accurate temperature forecasting is crucial to prevent frost heave and ensure stability. Its superior predictive capability, particularly for varying subgrade depths, makes it a valuable tool for engineers and planners involved in the design and maintenance of roadways in cold climates. By integrating temperature, water content, and frost heave as inputs, this approach also holds potential for optimizing subgrade maintenance schedules and improving the durability of seasonally frozen infrastructure. Accurate prediction of subgrade temperatures in seasonally frozen regions is crucial for understanding thermal states, frost heave phenomena, stability, and other critical characteristics. This study employs a nonlinear autoregressive with exogenous input (NARX) network to predict short-term subgrade temperatures in the Golmud-Nagqu section of China's National Highway 109. The methodology involves preprocessing subgrade monitoring data, including temperature, water content, and frost heave, followed by developing a temperature prediction model. This tailored NARX neural network, compared to the traditional BP neural network, integrates feedback and delay mechanisms for monitoring data, offering superior memory and dynamic response capabilities. The precision of the NARX model is assessed with the backpropagation (BP) network, indicating that the NARX neural network significantly outperforms the BP model in both precision and stability for temperature prediction in seasonally frozen subgrades. These findings suggest that the NARX model is a valuable tool for accurately predicting subgrade temperatures in seasonally frozen regions, offering significant insights for practical engineering applications. [ABSTRACT FROM AUTHOR]

Artificial ground freezing technology is the most important construction method of complex water-bearing soft clay rock. The thermodynamic properties of soft clay rock are important evidence for the design and construction of space resources development, and the variable hydrothermal parameter can directly affect the uncertain thermodynamic properties of soft clay rock. In this work, an array of field experiments on the soft clay rock are carried out, and the anisotropic spatial variations of hydrothermal parameters of soft clay rock are obtained. The statistical variability characteristics of variable hydrothermal parameters are estimated. A stochastic coupling model of soft clay rock with heat conduction and porous flow is proposed, and the uncertain thermodynamic properties of soft clay rock are computed by the self-compiled program. Model validation with the experimental and numerical temperatures is also presented. According to the relationship between anisotropic spatial variations and statistical variability characteristics for the different random field correlation models, the effects of the autocorrelation function, coefficient of variation, and autocorrelation distance of variable hydrothermal parameters on the uncertain thermodynamic properties of soft clay rock are analyzed. The results show that the proposed stochastic analysis model for the thermal characteristics of soft clay rock, considering the spatial variability of frozen soil layers, is scientifically reasonable. The maximum standard deviation of average thickness is 2.33 m, and the maximum average temperature is 2.25 °C. For the autocorrelation function, the most significant impact comes from DBIN. For the coefficient of variation, the most significant impact comes from thermal conductivity. Different variations of hydrothermal parameters have different effects on the standard deviation of soft clay rock temperature. The biggest influence is the thermal conductivity, while the lowest influence is the specific heat capacity. [ABSTRACT FROM AUTHOR]

To investigate the development of temperature fields under seepage conditions for pipe curtain freezing method, drawing on the Sanya River Estuary Trench Tunnel freezing project, combined with Darcy's law and heat transfer theory in porous media, using finite element software to establish a coupled water-heat numerical model, the study employs varying seepage rates in the model and a method for creating temperature measurement paths, and analyzes the evolution of the frozen soil curtain, circulation time, and wall thickness. The results indicate that the frozen soil curtain develops along the seepage direction, with the soil on the downstream side freezing earlier than the upstream side, and attaining a lower final temperature； when the flow rate is approximately 2. 87 m/d, the impact of low seepage rates on the overall circulation time of the frozen soil curtain is relatively minor； as the seepage rate increases, the overall circulation time of the frozen soil curtain grows significantly, accompanied by increased regional unevenness and a decrease in thickness； when the flow rate increases to approximately 10. 02 m/d, local non-circulation occurs in the frozen soil curtain. Considering the original freezing plan to be conservative, an optimized design is proposed： reducing the number of inner circle freezing pipes from 80 to 56, the simulated average thickness of the frozen soil curtain is approximately 4. 28 m, a decrease of 0. 195 m compared to the original plan. This optimized design still meets the freezing design specifications. [ABSTRACT FROM AUTHOR]

Combined with the freezing project of a contact channel of Taipei Metro, a three-dimensional numerical transient model is established by using COMSOL finite element software to carry out an in-depth study on the development law of the frozen soil curtain and the temperature field of the project, and a dynamic simulation is carried out to simulate the process of the change of the temperature field. The simulation results show that when the freezing tubes are arranged radially, the density of freezing tubes has a very significant effect on the freezing effect, and the denser the freezing tubes are, the better the freezing effect is； the intersection time of the freezing wall becomes the decisive moment for the rapid increase of freezing deformation, and the intersection time of the freezing wall is around the 15th day under the designed freezing scheme； by simulating the development of frozen soil curtain, the weakest area in the entire frozen soil curtain is the freezing area on the right side of the escape shaft, and it is recommended to increase the number of freezing tubes to strengthen the freezing effect in this area； the cooling curves of the three paths of temperature measure‐ ment points （DJ-1, DJ-2, DJ-3. Path DJ-1 is located outside the freezing area, Path DJ-2 is located near the freezing tubes, and DJ-3 is located in the inner part of the freezing curtain area） show that the further the distance from the freezing tubes the worse the freezing effect is, and the slower the temperature drop is. The average thickness and average temperature of the whole frozen soil curtain meet the freezing design requirements, which verifies that it is reasonable to adopt the contact channel freezing method. [ABSTRACT FROM AUTHOR]

The freezing strain characteristics of unsaturated soil are quite different from those of saturated soil. Besides the commonly observed frost heave, unsaturated soil may also experience frost shrinkage, causing uneven surface deformation and deterioration of soil properties. Matric suction and water–ice phase change are key factors affecting the freezing strain characteristics of soil. In this study, the freezing strain characteristics and underlying mechanisms of lean clay samples with different initial matric suctions at varying temperatures were investigated. A mathematical relationship between soil temperature and matric suction was established, enabling the estimation of variation trends in matric suction. The internal mechanisms of different freezing strain characteristics were analyzed based on the mesoscopic structures of frozen samples with low and high initial matric suctions. The results showed that samples with low initial matric suction and frozen at low negative temperatures are prone to frost heave. Frost heave occurs when the volume expansion of the soil caused by water–ice phase change exceeds the volume reduction due to increased matric suction; otherwise, frost shrinkage occurs. The morphology of pore ice in samples with different initial matric suctions varies, reflecting the degree of water–ice phase change in the soil. Using the Pearson correlation coefficient method, an empirical model for axial freezing strain applicable to unsaturated frozen lean clay was established, and the model's validity was confirmed with experimental data. [ABSTRACT FROM AUTHOR]

The phenomenon of water–ice phase transition in frozen soils is the key to explaining the mechanism of frost heaving and thawing settlement disaster. However, numerical analysis of water–ice phase transitions in frozen soils at mesoscale is rarely reported. This study combines the modified Gibbs-Thomson equation and the enthalpy-based lattice Boltzmann model, and develops a mesoscale numerical method to simulate the water–ice phase transition in the local pores of saturated frozen soil during freezing and thawing process. In order to accurately simulate this process, a new η coefficient is proposed to modify the Gibbs-Thomson equation, which is unrelated to the type of soil sample and gradation characteristics. According to the particle size distribution curve, the two-dimensional random circle generation method is used to reconstruct the soil pore structure. The freezing and thawing processes are verified with the experimental data. A larger non-uniformity coefficient Cu and curvature coefficient Cc of the grain size distribution result in a lower degree of subcooling and lower residual water content of the soil during the freezing process. The new model provides an effective means to understand the water–ice phase transition in frozen soil at a mesoscopic scale. [ABSTRACT FROM AUTHOR]

Weakly exothermic polymer grouting materials are used to repair the thaw settlement of roads in permafrost regions. In this study, the heat release characteristics of these materials were tested, and a visual polymer grouting model box consisting of steel plating and transparent acrylic glass was developed to conduct the model test of water and heat transfer in frozen soil. Based on the control equation of the water–heat coupling transfer in frozen soil, an analysis model of water–heat coupling in frozen soil was established, and the water–heat transfer process in frozen soil under exothermic conditions of the polymerization reaction of weakly exothermic polymer grouting materials was studied. The results demonstrate a power function relationship between the curing reaction temperature threshold and the density of weakly exothermic polymer grouting materials at different temperatures. The influence of the polymerization exothermic reaction on the moisture content and heat of frozen soil can be divided into two processes: thawing and freezing. The thawing process can be divided into three stages: slow, fast, and stable thawing. The maximum thawing depth of frozen soil has a positive correlation with the amount of grouting and the grout–soil contact area and a negative correlation with the water content of frozen soil. The initial temperature of frozen soil is selected as the common influence factor, and the prediction model of the influence of the amount of grouting, grout–soil contact area, and frozen-soil mass moisture content on the water content and heat of frozen soil is established. During the freezing process, with the continuous effect of low ambient temperature, liquid pore water at the thawing front will be refrozen. Therefore, in an actual project of the weakly exothermic polymer grouting repair of a subgrade in a permafrost region, the thermal disturbance of polymerization exothermic to the frozen subgrade can be further weakened by delaying the opening time to traffic. [ABSTRACT FROM AUTHOR]

Copyright of Scientia Iranica. Transaction D, Computer Science & Engineering & Electrical Engineering is the property of Scientia Iranica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Exposed to seasonal climate changes, the loess in the Ili region of Xinjiang, which has variable engineering properties, frequently undergoes freezing–thawing (F-T) and wetting–drying (W-D) cycles. In the present research, a series of uniaxial compression tests were conducted to investigate the collapsibility characteristics of the representative loess slope in the Ili region. In parallel, scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) tests were conducted. The test results obtained from the research indicated that both F-T cycles and W-D cycles exacerbate the deterioration of the loess, with the most severe effects observed after 6–10 cycles. Under the combined physical cycles, the microstructure of the loess progressively evolves from the relatively aggregated state to the dispersed one. Meanwhile, the porosity of the loess exhibited an initial increase with the number of W-D cycles, followed by an obvious decrease. Note that the pattern of the loess experiences fluctuation, which was achieved at the given point with the increased number of F-T cycles. It is suggested that the variability in loess wetting collapse is attributed to the irreversible alteration in the microstructure attributed to the combined cycles. The main reasons for the occurrence of loess collapse are the frost heaving force and the swelling–shrinking action. The impacts of W-D and F-T cycles on the loess obtained from this research can make a contribution to the in-depth understanding about loess collapse in the Ili valley. [ABSTRACT FROM AUTHOR]

Protecting soils during forest operations is important, especially soils with limited bearing capacity that are being harvested during the wet months. These soils can sustain damage to their structure, and therefore site productivity can be reduced. Climate change may change weather patterns, and less frozen soil conditions will occur more frequently, forcing planners to search for alternatives to overcome this challenge. In this context, cable-based systems for tree yarding are one option to reduce potential damage to soils and remaining stands. Time studies were performed on three cable yarding operations in the canton of Aargau, Switzerland, aiming to understand the performance of cable-based systems in flat terrain. A statistical analysis was performed, and costs were calculated. The yarding productivity was 13.92–21.86 cubic meters over bark (m3ob) per productive machine hour. The payload was identified as the main variable significantly influencing the productivity of a yarding cycle. Overall, installation procedures of the yarder were the most time-consuming and expensive work step. Production costs were 70–102 CHF m3ob−1 (corresponding to 73–107 € m3ob−1), including felling, yarding and roadside processing. This study confirms that the costs resulting from cable-based operations in flat terrain are high and the approach is not (yet) competitive with ground-based systems. [ABSTRACT FROM AUTHOR]

In Arctic landscapes, the active layer forms a near‐surface aquifer on top of the permafrost where water and nutrients are available for plants or subject to downslope transport. Warmer summer air temperatures can increase the thickness of the active layer and alter the partitioning of water into evapotranspiration and discharge by increasing the potential evapotranspiration, the depth to the water table, and changing the flow paths but the interacting processes are poorly understood. In this study, a numerical model for surface‐ and subsurface cryo‐hydrology is calibrated based on field observations from a discontinue permafrost area in West Greenland considered sensitive to future climate changes. The validated model is used to simulate the effect of three summers with contrasting temperature regimes to quantify the variations in the active layer thickness, the resulting changes in the water balance, and the implications on solute transport. We find that an increase of summer air temperature by1.6°C, under similar precipitation can increase the active layer thickness by 0.25 m, increase evapotranspiration by 5%, and reduce the total discharge compared to a colder summer by 9%. Differences in soil moisture and evapotranspiration between upslope and downslope were amplified in a warm summer. These hydrological differences impact solute transport which is 1.6 times faster in a cold summer. Surprisingly, we note that future warmer summer with increase in permafrost thaw may not necessary lead to an increase in discharge along a hill slope with underlying permafrost. Plain Language Summary: Precipitation that falls in the Arctic can be restricted from moving deeper into the subsurface by the permanently frozen soil that constraints water movement close to the surface in a layer that thaws every year during the summer. Warmer summers make this layer thaw deeper and water moves to deeper soil. In the deeper soil water moves more slowly as the material is more difficult to flow through, and thus also solute move slower. Moreover, the amount of water that returns to the atmosphere becomes higher with warmer temperatures. We measure soil conditions, and the velocity of solutes in the field along a hillslope in Greenland. Based on warm, average and cold years, we build a model capable of simulating storage and movement of water and the temperature in the soil. We use the model to test a warm, a normal, and a cold summer, and analyze the effects on the amount of water that reaches the end of the hillslope. We show that less water will move across the slope in warmer summers, but solutes travel at a higher velocity, and that cold summers have only a small effects on the movement of this solute. Key Points: Warmer summers reduce discharge from hillslope by 35%Solute movement is non‐uniform and controlled by precipitation eventsWarmer summers amplify differences between up‐ and downslope [ABSTRACT FROM AUTHOR]

The salt‐affected Soil‐Plant‐Atmosphere Continuum (SPAC) is a dynamic, interactive system that is particularly complex in seasonally frozen regions where salt transport, precipitation‐dissolution, and soil freeze‐thaw processes play crucial, interrelated roles. Understanding these coupled processes and representing them with mathematical models is critical for effective management of SPAC systems. This study presents a new mechanistic approach and an improved model that integrates a chemical equilibrium module within a mechanistic‐based transport computational module (modified SHAW model). The chemical equilibrium module determines salt precipitation‐dissolution using thermodynamic theory and explains the effects of efflorescence and subflorescence on system dynamics. The model enables simultaneous solutions for heat, water, and salt transport with chemical equilibrium throughout non‐freezing and freezing seasons, as well as plant growth dynamics. Assessment of the model using laboratory experiments and field studies showed good performance, with coefficient of determination values exceeding 0.65 for simulated and measured evaporation rate, leaf area index, soil water content, salt content, and temperature. Furthermore, a comparison between simulation results considering and neglecting the impact of salt precipitation‐dissolution highlights potential inaccuracies in soil heat‐water‐salt dynamics and plant water use resulting from the omission of this process in mechanistic models. Key Points: New soil‐plant‐atmosphere model integrates an equilibrium module into a mechanistic‐based transport moduleModel simulates plant growth and soil heat‐water‐salt dynamics in seasonally frozen regionsInaccuracies arise in modeling soil heat‐water‐salt dynamics and plant water use resulting from omitting salt precipitation‐dissolution [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Common parametrizations of soil hydraulic properties rely on unimodal curves, which cannot accurately represent the properties of many macroporous, aggregated, mixed, or compacted soils. Multimodal hydraulic curves are increasingly used to represent these structured soils in eco‐hydrological models, but the dynamics of the processes that shape soil structure—and the resulting dynamics of soil hydraulic properties—are often neglected. In cases such as compaction recovery, where the structure‐shaping process can be modeled, coupling the evolving pore volumes to soil hydraulic properties in a physically based way remains challenging. Here, we show how modeled or estimated soil structure evolution, when expressed as a time series of porosities in a few pore size classes, can be assimilated into established models of soil hydraulic properties. Our method relies on the division of retention models into smooth segments, whose water contents can be independently adjusted. We apply the approach to examples of modeled soil structure evolution from the published literature: one describing soil structure recovery after compaction and one describing structure formation as a result of organic amendment. In the cases considered, the estimated soil hydraulic conductivity varies more strongly than the modeled porosity which drives it. This shows that transport‐related soil functions can be impacted longer (after compaction) or sooner (after amendment) than suggested by the evolution of structural metrics such as porosity. In general, modeling the evolution of soil hydraulic properties in cases such as these paves the way for holistic, process‐based modeling of land management practices and their impact on soil functioning. Core Ideas: We show a method for dividing existing retention curves into smooth sub‐curves corresponding to pore size classes.To represent an evolving soil structure, we scale the sub‐curves and sum them to form a composite retention curve.We estimate the effect of (de)compaction on permeability using the composite retention curve and the Mualem model.We apply the approach to modeled response of soil structure to mechanical compaction and to organic amendments. Plain Language Summary: Computer simulations of water propagation in the soil allow researchers to assess the risk of floods, optimize the irrigation of crops, or understand the effects of climate change on food production and water availability. These simulations use mathematical functions to describe how much water is stored in the soil and how fast it flows under different conditions. Over the course of a typical simulation, these functions do not change, which makes it difficult to account for processes that significantly affect the capacity of soil to store and conduct water, such as soil freezing, plowing, spreading of manure, or the compression of soil by heavy machinery. Here, we introduce soil water storage and conductivity functions that can evolve in time as dictated by simulations or measurements of such soil‐changing processes. Using these functions, we show that soil water propagation may be affected sooner after spreading amendments and longer after soil compaction than previously thought. [ABSTRACT FROM AUTHOR]

The influence of cyclic loading on frozen soil may be reflected by the variation of soil temperature. To uncover this process, dynamic triaxial tests were performed in this study on saturated warm frozen soil, during which the temperature changes inside the specimens were monitored. The effects of initial dry density, test temperature, dynamic stress amplitude and vibration frequency on temperature change were studied. The results universally manifested a rise in specimen temperature under cyclic loading. The higher dynamic stress, vibration frequency, testing temperature and initial dry density was responsible for the faster heating rate. The mechanism controlling the temperature variation inside the specimens could be explained by the heat production as a result of friction and extrusion between soil grains when subjected to dynamic loading. This temperature rise could be compromised by the heat transfer with the thermal environment where the specimen was in. A colder environment would cause the specimen temperature to drop back. This study provides an experimental foundation for deeply understanding how the mechanical behavior of frozen soil degrades under dynamic loading. [ABSTRACT FROM AUTHOR]

Though a comprehensive in situ measurement project, the performance of a deep pit-in-pit excavation constructed by the top-down method in seasonal frozen soil area in Shenyang was extensively examined. The measured excavation responses included the displacement of capping beam and retaining pile, settlement of ground surface, and deformation of metro lines. Based on the analyses of field data, some major findings were obtained: 1) the deformations of retaining structures fluctuated along with the increase of temperature, 2) the deformation variation of retaining structures after the occurrence of thawing of seasonal frozen soil was greater than that in winter, although the excavation depth was smaller than before, 3) the influence area of ground settlement was much smaller because of the features of seasonal frozen sandy soil, 4) the displacement of metro line showed a significant spatial effect, and the tunnel lining had an obviously hogging displacement pattern, and 5) earth pressure redistribution occurred due to the combined effects of freezing-thawing of seasonal frozen soil and excavation, leading to the deformation of metro line. The influence area of ground settlement was obviously smaller than that of Shanghai soft clay or other cases reported in literatures because of special geological conditions of Shenyang. However, the deformation of metro lines was significantly lager after the thawing of the frozen soil, the stress in deep soil was redistributed, and the metro lines were forced to deform to meet a new state of equilibrium. [ABSTRACT FROM AUTHOR]